A high-speed intersubband modulator based on quantum interferencein double quantum wells

Calculations on a modulator based on quantum interference in AlGaAs/GaAs asymmetric double quantum wells (QWs) are performed. The modulation of the absorption is based on the anti-crossing behavior of the two lowest states in the coupled wells. At anti-crossing, the oscillator strengths of the transitions from these two lowest states to a higher state are changed in opposite directions. The width of the barrier between the wells should be thick enough to allow a large change in oscillator strength with applied field, yet thin enough so that the absorption peaks of the transitions are resolved. The QWs are designed so that one absorption peak has only a small energy shift for the transition used for modulation while the absorption varies rapidly with the applied voltage. A complete structure including a surface plasmon waveguide is proposed enabling calculations of modal absorption. Parameters important for the performance of the modulator are then determined. An extinction ratio of 10 dB at a wavelength of 8.4 μm is predicted for a device length of 18 μm and a peak-to-peak voltage of 0.9 V. The resistance-capacitance-limited 3-dB bandwidth is 130 GHz. The predicted performance compares very favorably with present interband modulators based on the quantum-confined Stark effect     

Fermi-Level Pinning in Nanocrystal Memories

The nanocrystal (NC) work-function engineering, which plays an important role on the NC memory characteristics such as memory window and retention time, were long regarded as a matter of choice on NC materials. In this letter, we report opposite polarities of charge storage in Au NC memories with different control oxides. The effective NC work function is found to be not only a bulk property of the NC, but also governed by the interface with surrounding dielectric, as a result of the Fermi-level pinning. By replacing Au NCs with C₆₀ molecules, we also show the pinning effect generally exists at quantum-dot-based devices with high density of interface states. This fundamental interface property should be taken into account in the selection of NC and dielectric materials for the NC memory optimization     

Generalized Approach towards Secretion-Based Protein Production via Neutralization of Secretion-Preventing Cationic Substrate Residues

Many heterologous proteins can be secreted by bacterial ATP-binding cassette (ABC) transporters, provided that they are fused with the C-terminal signal sequence, but some proteins are not secretable even though they carry the right signal sequence. The invention of a method to secrete these non-secretable proteins would be valuable both for understanding the secretory physiology of ABC transporters and for industrial applications. Herein, we postulate that cationic “supercharged” regions within the target substrate protein block the secretion by ABC transporters. We also suggest that the secretion of such substrate proteins can be rescued by neutralizing those cationic supercharged regions via structure-preserving point mutageneses. Surface-protruding, non-structural cationic amino acids within the cationic supercharged regions were replaced by anionic or neutral hydrophilic amino acids, reducing the cationic charge density. The examples of rescued secretions we provide include the spike protein of SARS-CoV-2, glutathione-S-transferase, streptavidin, lipase, tyrosinase, cutinase, growth factors, etc. In summary, our study provides a method to predict the secretability and a tool to rescue the secretion by correcting the secretion-blocking regions, making a significant step in understanding the physiological properties of ABC transporter-dependent protein secretion and laying the foundation for the development of a secretion-based protein-producing platform.     

环锭纺的发展潜力

目前存在3个关键因素导致环锭纺产量无法进一步提高。介绍了一些有利于未来环锭纺技术进一步发展的基本情况。详细分析了环锭纺工序中的能耗问题,这是性能能否提高的基础。环锭纺产量的提高,不仅是技术上是否可行的问题,更重要的是能够获得良好的经济效益。     

Isostere Adsorptionswärme des Ethans an Zeolithen vom Typ NaX und NaY

Isosteric Heat of Adsorption of n-Ethane on Zeolites NaX and NaY Using a volumetric method isotherms of adsorption of ethane on zeolites NaX and NaY were measured. The Clausius-Clapeyron equation was used to calculate the isosteric heat of adsorption of the paraffin on both molecular-sieves. These enthalpies show a linear dependence of the amount of adsorbed molecules. The zeolite with the higher charge density shows a larger heat of adsorption. The difference in the heat of adsorption is explained by adsorption on different centers in the cavity of both zeolites.     

LANDSAT TM image forward/reverse scan banding: characterization and correction

Cross-scan averages of forward and reverse scan are analysed to model the within-line sample-position-dependent noise of LANDSAT Thematic Mapper images, in cases where no radiometric saturation is present. Two sources of banding are discussed: the droop, already mentioned by other authors, and the so-called radiometric hysteresis. The defined models are used to generate a correction algorithm which has been tested with real data.     

Technical note Development of a new technique for geological investigation using DTM data: An example in western Turkey

The topographic features formed by factors such as altitude, tectonic movement, lithology and others were analysed quantitatively by a new technique in this study on rift valleys in western Turkey. This technique calls for the determination of the altitude and vertical geologic movements in long-wavelength components after the separation of the short- and long-wavelength components of the two-dimensional Fast Fourier Transform (FFT) based on a digital terrain model (DTM). The location of active faults can be inferred from the magnitude of the anomalies of altitudinal dispersion and the position of the anomalies, and it is also inferred that the values of the anomalies are related to the displacement of the faults. The results have been checked in the field and it was shown that this technique is very effective for structural analysis.